A buttweldpipefitting is designed to be welded on site at its end(s) to connect pipe(s) together and allow change in direction or pipe diameter, or branching or ending. This fitting then becomes part of a system for transporting fluids (oil, gas, steam, chemicals, ) in a safe and efficient manner, over short or long distances. STAINLESS BUTT WELD,SOCKET,THREAD PIPE FITTINGS SUPPLIER adk engineering co.,limited supply stainless steel buttweldpipefittings,threaded pipefittings,socket pipefittings and other pipefittings What are the differences between Socket weld and Butt weld? Socket Weld (SW) fittings are defined in the ASME B16.11. As with socket weld, a pipe is inserted into a recessed area of the fitting. Both the pipe and the fitting are square cut, with no need for beveled end or preparation other than cleaning the outside, which allows easy welding and installation.